I have a 95 325is with m50tu. It makes a "chirping" sound when idling or accelerating at low rpms, especially when cold. Replaced both belt tensioner pulleys and belts this weekend with no change. I noticed when doing it that I have no idler pulley on my car. I'm pretty sure I have a mechanical tensioner like this:

not my car, found this on an e30 forum i'm on (this m50 is in an e30). he has an idler pulley mounted up.

according to realoem this style of tensioner (which is different than the hydraulic shock type also found on 95 m50s) does not use an idler/deflection pulley?